This invention relates to packaging machines, especially those of the type designed to apply and secure a web of material to containers, to cutting mechanisms for severing the web of material between adjacent containers, as well as to conveyors and container supports for such packaging machines.
It is well known to use a packaging machine to apply a continuous web of heat sealable film or other material to a series of containers supported on a conveyor. In such machines, it is necessary to separate or sever the continuous web of material between adjacent containers after the web has been applied and secured to the container. Various types of severing or cutting devices have been used in the past with such machines with varying success.
One prior known type of cutter includes opposed cutting blades which are reciprocated toward and away from one another in order to shear the web of material at the desired location. Another type of cutter is that shown in U.S. Pat. No. 3,851,445 and includes a slitter which is reciprocated diagonally across a moving conveyor to cut the web of material. A third type of cutter is a continuously rotated cutter such as those shown in U.S. Pat. Nos. 3,436,894 or 3,706,183. With each of the above types of cutting or slitting assemblies, complex timing devices such as belts, chains, gears or extensive levers or the like were necessary to enable the appropriate shearing, slitting or severing action to take place properly between adjacent containers so as to avoid damage to either the container or the web of material secured to the container.
A second problem encountered with the above type of packagers has been the inability or relative difficulty in modifying the packaging conveyor to support different sizes of containers. In the type of packager with which the present invention is concerned, open-topped, formed thermoplastic or paper containers are slipped in apertures in generally horizontally extending plates secured in some fashion to a conveyor which carries them under a web applying and securing structure. As is apparent, various sizes and shapes of containers require different support plates having different sizes or shapes of receiving apertures. In prior packaging machines or conveyors, a change in container supports required substantial time and effort including either changing the conveyor support chains or other supporting devices, separate securement of different size plates with threaded fasteners and support brackets to the prior existing chains, or other time-consuming procedures. This, in itself, was a difficult and laborious operation which often necessitated a packaging concern to purchase two or three different packagers each with its own size container support plates in order to avoid the time-consuming job of changing container supports.
The above changover problems also resulted in problems with the cutting, shearing or slitting apparatuses for the continuous web material. In prior machines, if the container supports were changed or their locations modified to support different sizes of containers, adjustment and retiming of the cutting apparatus was also necessary. That is, either the chains, gears or levers which timed the shearing, slitting or continuously rotating cutting action of the prior known cutting assemblies had to be changed so that the cutting action occurred at the proper place and time with respect to the new container supports. This, too, added further time and labor expense to the conversion of the packager from one size container support to another.
In addition to the above problems, prior packaging machines utilized web-cutting assemblies which were often very complex and required frequent sharpening or normal maintenance even when the container supports were not changed. This resulted in frequent downtime for the packager and additional expense for repairs.
In my prior application, Ser. No. 904,216, now U.S. Pat. No. 4,196,561, a rotatable cutter was disclosed and claimed including camming means at one end engaging a single projection on each of a plurality of successive container support members for rotating the cutter and distinct blades thereon between successive container support member. It was found that at certain times the cutter assembly would not be sufficiently rotated following severance of the web to allow proper engagement of the camming means with the projection on the next successive container support member. This resulted in machine jamming at certain times.
Also, it was found in the prior packaging machine disclosed in Ser. No. 904,216, wherein container support pins were included at each joint of each conveyor chain, that certain of the conveyor pins could be eliminated thereby reducing the expense of such chains while retaining the ability to provide cutoff of the web at various lengths including the 31/2, 4, 5 and 7 inch cutoff lengths used in the packaging industry.
Also, in attempting to reduce the cost of container supports through molding from plastics or other materials, it was discovered that supports formed from settable materials such as moldable plastics were more flexible than prior known metallic container supports. The flexibility of such molded materials caused problems in proper sealing of the web materials to the container tops since the container supports flexed under the pressure of the web applying devices during packaging. Accordingly, proper sealing of the open-top containers with the web applying devices would not result with molded container support embodiments.
The various aspects of the present invention were conceived in recognition of and as solutions for the above problems, as well as improvements for my prior packaging machines.